用户报告说计算机工作越来越慢了，首先应该采取以下哪种措施？（）

A、格式化并重装硬盘

B、备份并重新恢复硬盘

C、增加一个新硬盘，并格式化为相同的文件系统

D、使用硬盘属性下的碎片整理程序

直放站提取信号源的主要方式有哪几种：（）

A、通过直放站的施主天线直接从附近基站提取信号。

B、用耦合器从附近基站耦合部分信号通过光纤传送到盲区内的直放站。

C、通过直放站的施主天线直接从附近直放站提取信号。

D、用耦合器从附近基站耦合部分信号通过电缆传送到盲区内的直放站。

Identify three situations in which you would NOT be able to drop a tablespace. （）

when the tablespace is online

when the tablespace has segments with data in it

when the tablespace is a default permanent tablespace for the database

when the tablespace contains a table that is currently being used by transactions

when the tablespace contains undo data that is needed to rollback an uncommitted transaction

肝叶切除术适用于（）

A、急性单纯性胆囊炎

B、胆囊结石经常发作

C、胆总管结石伴有休克

D、肝内结石局限于左叶

E、胆总管扩张不明显，但并发慢性胰腺炎

Which two statements about sequences are true? （）

You use a NEXTVAL pseudo column to look at the next possible value that would be generated from a sequence, without actually retrieving the value.

You use a CURRVAL pseudo column to look at the current value just generated from a sequence, without affecting the further values to be generated from the sequence.

You use a NEXTVAL pseudo column to obtain the next possible value from a sequence by actually retrieving the value from the sequence.

You use a CURRVAL pseudo column to generate a value from a sequence that would be used for a specified database column.

If a sequence starting from a value 100 and incremented by 1 is used by more then one application, then all of these applications could have a value of 105 assigned to their column whose value is being generated by the sequence.

You use REUSE clause when creating a sequence to restart the sequence once it generates the maximum value defined for the sequence.

You have executed this command to change the size of the database buffer cache： SQL> ALTER SYSTEM SET DB_CACHE_SIZE=2516582； System altered.  To verify the change in size， you executed this command： SQL> SHOW PARAMETER DB_CACHE_SIZE NAME TYPE VALUE  ------------------- ----------- ------------------  db_cache_size big integer 4194304  （4M）  Why is the value set to 4194304 and not to 2516582（）

A、because 4194304 is the granule size

B、because 4194304 is the standard block size

C、because 4194304 is the largest nonstandard block size defined in the database

D、because 4194304 is the total size of data already available in the database buffer cache